Pubertal induction and transition to adult sex hormone replacement in patients with congenital pituitary or gonadal reproductive hormone deficiency: an Endo-ERN clinical practice guideline

An Endo-European Reference Network guideline initiative was launched including 16 clinicians experienced in endocrinology, pediatric and adult and 2 patient representatives. The guideline was endorsed by the European Society for Pediatric Endocrinology, the European Society for Endocrinology and the European Academy of Andrology. The aim was to create practice guidelines for clinical assessment and puberty induction in individuals with congenital pituitary or gonadal hormone deficiency. A systematic literature search was conducted, and the evidence was graded according to the Grading of Recommendations, Assessment, Development and Evaluation system. If the evidence was insufficient or lacking, then the conclusions were based on expert opinion. The guideline includes recommendations for puberty induction with oestrogen or testosterone. Publications on the induction of puberty with follicle-stimulation hormone and human chorionic gonadotrophin in hypogonadotropic hypogonadism are reviewed. Specific issues in individuals with Klinefelter syndrome or androgen insensitivity syndrome are considered. The expert panel recommends that pubertal induction or sex hormone replacement to sustain puberty should be cared for by a multidisciplinary team. Children with a known condition should be followed from the age of 8 years for girls and 9 years for boys. Puberty induction should be individualised but considered at 11 years in girls and 12 years in boys. Psychological aspects of puberty and fertility issues are especially important to address in individuals with sex development disorders or congenital pituitary deficiencies. The transition of these young adults highlights the importance of a multidisciplinary approach, to discuss both medical issues and social and psychological issues that arise in the context of these chronic conditions.

Gonadal function in adult male patients with congenital adrenal hyperplasia

CONTEXT

Current knowledge on gonadal function in congenital adrenal hyperplasia (CAH) is mostly limited to single-center/country studies enrolling small patient numbers. Overall data indicate that gonadal function can be compromised in men with CAH.

OBJECTIVE

To determine gonadal function in men with CAH within the European 'dsd-LIFE' cohort.

DESIGN

Cross-sectional clinical outcome study, including retrospective data from medical records.

METHODS

Fourteen academic hospitals included 121 men with CAH aged 16-68 years. Main outcome measures were serum hormone concentrations, semen parameters and imaging data of the testes.

RESULTS

At the time of assessment, 14/69 patients had a serum testosterone concentration below the reference range; 7 of those were hypogonadotropic, 6 normogonadotropic and 1 hypergonadotropic. In contrast, among the patients with normal serum testosterone (55/69), 4 were hypogonadotropic, 44 normogonadotropic and 7 hypergonadotropic. The association of decreased testosterone with reduced gonadotropin concentrations (odds ratio (OR) = 12.8 (2.9-57.3)) was weaker than the association between serum androstenedione/testosterone ratio ≥1 and reduced gonadotropin concentrations (OR = 39.3 (2.1-732.4)). Evaluation of sperm quality revealed decreased sperm concentrations (15/39), motility (13/37) and abnormal morphology (4/28). Testicular adrenal rest tumor (TART)s were present in 39/80 patients, with a higher prevalence in patients with the most severe genotype (14/18) and in patients with increased current 17-hydroxyprogesterone 20/35) or androstenedione (12/18) serum concentrations. Forty-three children were fathered by 26/113 patients.

CONCLUSIONS

Men with CAH have a high risk of developing hypothalamic-pituitary-gonadal disturbances and spermatogenic abnormalities. Regular assessment of endocrine gonadal function and imaging for TART development are recommended, in addition to measures for fertility protection.

Psychosocial outcome in adult men born with hypospadias

INTRODUCTION

Hypospadias, which is a surgically treated congenital malformation of the male urethra, may have a negative impact on quality of life. This aspect has previously been subject to limited research. This study examined the long-term psychosocial outcome of a large cohort of adult males born with hypospadias.

OBJECTIVE

The purpose of this case-control study was to assess a possible negative influence on the psychosocial outcome in adult males with hypospadias.

STUDY DESIGN

Males with hypospadias treated in Sweden and aged ≥18 years old participated in this follow-up study. Age-matched men and university students were recruited as controls. The participants answered a questionnaire designed to reflect the subjective quality of life, social factors, need of support and follow-up, and the perceived impact of the disease upon upbringing. It also looked at the validated Psychological General Well-Being (PGWB) questionnaire and Relationship Questionnaire (RQ).

RESULTS AND DISCUSSION

A total of 167 patients (median age 34 years, 63% distal, 24% mid, and 13% proximal hypospadias) and 169 controls (median age 33 years) participated in the study. Patients had their first operation at 4 years of age (median) and the median follow-up time was 29 years following the first surgery. Men with hypospadias had a comparable total quality of life level with a mean total PGWB score of 82 (normal range 78-83) compared with 85.6 in controls. Scores on wellbeing and vitality were lower, even if the differences were small. Hypospadias did not affect marital status, presence of children in the family, frequency of employment or experience of bullying. These men more often lived at home with their parents (P=0.001) and had a lower level of education (P=0.004), even if the educational level in both patients and controls was high compared with the general Swedish population. Patients with proximal hypospadias were shorter compared with controls (P=0.003), which was consistent with the prenatal growth restriction associated with hypospadias. The group with proximal hypospadias expressed a greater need for medical (45.5%) follow-up compared with mid (28.2%) and distal (18.1%) cases (P=0.001). Patients with proximal hypospadias tended to avoid close relationships because of fear of being hurt.

CONCLUSIONS

The findings suggested that patients treated for hypospadias have a good HRQoL, can be expected to have a normal psychosocial life, and marry and have children. Repeated follow-up and psychological support during childhood/adolescence is however of great importance for patients with more proximal hypospadias.

Neuropsychological Development in Patients with Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase (LCHAD) Deficiency

BACKGROUND

Reports on cognitive outcomes in long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) are scarce. We present results from neuropsychological assessments of eight patients diagnosed with LCHADD prior to newborn screening with regard to clinical disease severity.

METHODS

Intellectual ability and adaptive and executive functions were assessed using age-appropriate Wechsler Scales, Adaptive Behavior Assessment Scales (ABAS), and Behavior Rating Inventory of Executive Function (BRIEF).

RESULTS

Five patients performed in the normal range on IQ tests but with lower scores on verbal working memory. In addition, they had lower parent-rated adaptive and executive functions.Three patients had intellectual disabilities with IQs below normal and/or autism spectrum disorders. In addition, they had low results on parent-rated adaptive functions. (Two of these patients had epilepsy.) Conclusions: Patients with LCHADD seem to have a specific cognitive pattern, with presentation as intellectual disability and specific autistic deficiencies or a normal IQ with weaknesses in auditive verbal memory and adaptive and executive functions. Future studies are warranted to investigate whether newborn screening programs and early treatment may promote improved neuropsychological development and outcomes.

Psychosocial Factors in Disorders of Sex Development in a Long-Term Perspective: What Clinical Opportunities are there to Intervene?

Disorders or differences in sex development (DSD) comprise a wide spectrum of severity. The overall goal for the treatment and care is good quality of life but current knowledge concerning the psychosocial situation and health related quality of life for patients with different forms of DSD is limited. Follow-up studies have often focused on surgical results, sexual function, and psychosexual outcome and indicated unsatisfactory results in many cases. Epidemiological studies show less than optimal psychosocial situation for some of the diagnostic groups. Studies indicate that access to psychological support and understandable information is important for the outcome. Hormonal and surgical treatments are improving and new and better ways to strengthen the patient's ability to cope with the situation are needed. In a well-functioning multidisciplinary team, the patient's and family's needs should be identified. Tools to accomplish this can be developed. The care and our knowledge about disorders of sex development have developed considerably during the last decade. These are small patient groups with rare conditions that require specialized, highly qualified care in all aspects: medical, surgical, and psychological. It is important that changes in treatment practice are continuously evaluated.

Increased and early lipolysis in children with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency during fast

Children with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHAD) have a defect in the degradation of long-chain fatty acids and are at risk of hypoketotic hypoglycemia and insufficient energy production as well as accumulation of toxic fatty acid intermediates. Knowledge on substrate metabolism in children with LCHAD deficiency during fasting is limited. Treatment guidelines differ between centers, both as far as length of fasting periods and need for night feeds are concerned. To increase the understanding of fasting intolerance and improve treatment recommendations, children with LCHAD deficiency were investigated with stable isotope technique, microdialysis, and indirect calometry, in order to assess lipolysis and glucose production during 6 h of fasting. We found an early and increased lipolysis and accumulation of long chain acylcarnitines after 4 h of fasting, albeit no patients developed hypoglycemia. The rate of glycerol production, reflecting lipolysis, averaged 7.7 ± 1.6 µmol/kg/min, which is higher compared to that of peers. The rate of glucose production was normal for age; 19.6 ± 3.4 µmol/kg/min (3.5 ± 0.6 mg/kg/min). Resting energy expenditure was also normal, even though the respiratory quotient was increased indicating mainly glucose oxidation. The results show that lipolysis and accumulation of long chain acylcarnitines occurs before hypoglycemia in fasting children with LCHAD, which may indicate more limited fasting tolerance than previously suggested.

Suboptimal psychosocial outcomes in patients with congenital adrenal hyperplasia: epidemiological studies in a nonbiased national cohort in Sweden

CONTEXT

Congenital adrenal hyperplasia (CAH), CYP21A2 deficiency, results in cortisol and aldosterone deficiency and increased production of androgens, with a good genotype phenotype correlation.

OBJECTIVE

The objective of the investigation was to study psychosocial outcomes in relation to clinical severity, CYP21A2 genotype, in men and women.

DESIGN

This was an epidemiological study with a matched case control design.

SETTING

The setting of the study was all known CAH patients in Sweden.

PARTICIPANTS

Five hundred eighty-eight patients, more than 80% with known severity of CAH, and 100 controls per patient matched for sex, year, and place of birth participated in the study.

MAIN OUTCOME AND MEASURES

Proxies for quality of life were selected: level of education, employment, income, sick leave, disability pension, marriage, and children.

RESULTS

Women with salt-wasting (SW) CAH had completed primary education less often [odds ratio (OR) 0.3], not explained by neonatal salt crisis or hypoglycemia because the men did not differ from controls. Men and women in the less severe I172N genotype group were more likely to have an academic education (OR 1.8). SW women were more likely to have an income in the top 20th percentile (OR 2.0). Both men and women had more disability pension (OR 1.5) and sick leave (OR 1.7). The men more often had long-lasting employment (OR 3.1). Men were more often (OR 1.6) and women were less often married (OR 0.7). Patients had children less often (OR 0.3).

CONCLUSIONS

This study shows important outcome differences regarding education; employment; marriage and fertility, depending on sex; and severity of CAH. The mechanisms behind this and the increased risk for sick leave or disability pension in both men and women should be identified to improve medical and psychological care.

Growth in Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is an inborn error of fatty acid metabolism that affects the degradation of long chain fatty acids and causes insufficient energy production and accumulation of toxic intermediates. The treatment consists of a diet low in fat, with supplementation of medium-chain triglycerides that bypass the metabolic block. In addition, frequent feeds and extra carbohydrates are given during febrile illnesses to reduce lipolysis. Hence, this diet differs from the general dietary recommendations for growing children. Furthermore, the Swedish dietary instructions for fat intake in LCHAD deficiency are given in grams, which differ from most guidelines that recommend fat intake as percentage shares of total caloric intake.

AIMS

To assess growth in patients with LCHAD deficiency, in relation to dietary treatment and to evaluate if overweight/obesity is more common than in the normal population.

RESULTS

The growth velocity showed acceleration after diagnosis and the start of treatment, followed by a period of stable or decelerated growth. The majority of the patients developed overweight to a greater extent than children without LCHAD deficiency. Several patients also went through a phase of obesity. Data on final height (FH) showed that three out of five patients had grown according to their genetic potential.

CONCLUSIONS

Regular and frequent follow-up and careful monitoring of weight are essential to avoid the development of overweight and obesity. The Swedish dietary instructions defining fat intake in total grams per day may be an alternative approach to achieve a moderate total caloric intake.

Disorders of sex development

Infants born with ambiguous genitalia represent a complex clinical challenge. A systematic clinical investigation aims at determining the hormone production and which anatomical structures are present in order to understand at what level the sex differentiation has been affected; chromosomal, gonadal or hormonal synthesis and action levels. The increased genetic knowledge in the field has opened up new diagnostic possibilities. Sex development requires the balanced and sequential activation of transcription factors, signaling molecules and hormones. It has recently been shown that not only testis but also normal ovarian development is an active process. Genes involved in gonadal disorders of sex development often act in a gene dosage-dependent manner, with different effects in XY or XX embryos. The management of patients with disorders of sex development, including decisions about sex of rearing, must be carried out by a specialized multidisciplinary team and include an extended genetic investigation as well as psychological considerations.

FC14-02 - Biological stress markers, executive functions and self-perceived stress in adults with ADHD (attention-deficit /hyperactivity disorder)

Introduction

The management of normal daily tasks may be complicated for adults with ADHD (attention-deficit/hyperactivity disorder) due to executive dysfunctions. ADHD may thus increase the risk of chronic stress in everyday life.

Objective

To study endocrinological and psycho physiological stress markers in adults with ADHD in association to performance in test of executive functions (EF) and self-perceived stress.

Methods

Cardiovascular stress markers were assessed in 30 adults with ADHD with no psychoactive medication, and 30 healthy controls during: (1) non-stress baseline; (2) cognitive stress; and (3) non-stress recovery. The Visual Analogues Scale was used to assess self-perceived stress. Salivary cortisol was measured pre- and post-experiment. To measure stress in everyday life we assessed diurnal cortisol values, stressors and self-ratings of stress.

Results

The group with ADHD showed higher self-perceived stress but attenuated or atypical cardiovascular stress reactivity during experimentally induced stress, and stress reactivity predicted performance in the executive test. Baseline cardiovasular values did not differ from the controls. The diagnosis of ADHD significantly increased the risk of belonging to the group with high post-stress cortisol levels. The two groups were comparable with respect to overall diurnal cortisol levels and rhythm. The ADHD group reported significantly higher self-perceived stress and these values correlated with level of stressors in everyday life.

Conclusions

The overall baseline values in biological stress markers may be comparable between adults with ADHD and healthy controls, while the stress reactivity and recovery pattern may differ between the two groups.

A trial with N-carbamylglutamate may not detect all patients with NAGS deficiency and neonatal onset

N-acetylglutamate synthase (NAGS) deficiency is a rare urea cycle disorder. An effective treatment, N-carbamoyl-L-glutamic acid (NCGA), is now available, increasing the importance of identifying and treating these patients early. We describe a case with genetically verified NAGS deficiency and neonatal onset of severe hyperammonaemia. The ammonia levels increased above 1400 micromol/L. The patient did not respond to NCGA treatment during the first 15 h, indicating that a delayed response or no response cannot be used as a safe indicator for excluding NAGS deficiency in the acute situation. Hence, conventional treatment should not be delayed by a diagnostic procedure, such as a loading test. Furthermore, at 3 years of age this patient has normal psychomotor development, underlining the possibility of a favourable outcome despite markedly elevated ammonia levels, coma, and seizures in the neonatal period. Including NCGA early in the treatment of patients with hyperammonaemia may be of clinical importance. In order to detect patients with NAGS deficiency and neonatal onset and to optimize care, it is important to use the available treatment strategies to reduce plasma ammonia concentrations without delay. We propose the use of combined symptomatic treatment, i.e. glucose infusion, sodium benzoate, arginine or citrulline, and when indicated haemodialysis, as well as NCGA treatment in all neonates presenting with severe hyperammonaemia. The treatment should be continued until laboratory investigations are complete or indicate another disorder.

Female preponderance in congenital adrenal hyperplasia due to CYP21 deficiency in England: implications for neonatal screening

Congenital adrenal hyperplasia (CAH) due to 21-hydroxylase (CYP21) deficiency causes symptoms ranging from life-threatening neonatal adrenal crises to minimal virilization in adulthood. The relationship between CYP21 genotype and phenotypic markers in a non-screened population of 73 CAH children (44 female, 29 male; 54 white, 19 Asian) treated at the Royal Manchester Children's Hospital was investigated and ethnic and sex differences assessed. The patients were categorized according to the mutation on the mildest allele. The age at the time of diagnosis differed significantly between the groups (p = 0.02): all 25 Null and 25 of 26 of the I2 splice patients were diagnosed during the neonatal period, whereas 7 of 11 I172N patients were diagnosed late. Degree of female genital virilization, 17-hydroxyprogesterone level at diagnosis, and fludrocortisone requirement during the 1st year of treatment correlated with the genotype, although Asian Null patients required more fludrocortisone than their white counterparts (p = 0.055). There was an equal sex ratio in both the I2 splice (12 female/14 male) and I172N (5 female/6 male) groups. However, in the Null group, the ratio was 4.0 (20 female/5 male; p = 0.003), suggesting that some Null male infants perish before being clinically detected to have CYP21 deficiency. Our findings strongly support the need for implementation of a neonatal screening programme for CAH in the UK which may reduce the male infant mortality.

Neonatal screening for congenital adrenal hyperplasia: 17-hydroxyprogesterone levels and CYP21 genotypes in preterm infants

OBJECTIVE

Neonatal screening for congenital adrenal hyperplasia (CAH) among preterm infants is complicated by the fact that healthy preterm infants have higher levels of 17-hydroxyprogesterone (17-OHP) than term infants, resulting in a higher false-positive rate. Even when gestational age-related cutoff levels after ether extraction were used, the false-positive cases primarily comprised preterm infants. The aim of the study was to optimize the procedure for neonatal screening for CAH in preterm infants.

METHODS

The 17-OHP levels in 6200 preterm infants were correlated to the gestational age. We also calculated the number of recalls for different putative cutoff levels of the 17-OHP by direct assay and after extraction in 1275 preterm infants who represented the most elevated cases in a population of approximately 30 000 preterm infants. The CYP21 genotypes and screening levels were determined in the 12 preterm infants with CAH diagnosed since the start of screening. The effect of possible interfering factors such as gestational age, neonatal stress, and prenatal glucocorticoid treatment for pulmonary maturation was studied.

RESULTS

The extraction procedure did not significantly improve the sensitivity or specificity of the screening, whereas it delayed the day of recall from 8 to 13 days (median). We could not demonstrate any systematic influence of the studied stress factors or the prenatal glucocorticoid treatment on the 17-OHP screening levels. In the patients with CAH, the 17-OHP levels correlated better with disease severity than with the degree of prematurity.

CONCLUSIONS

On the basis of these results, we omitted the extraction step and changed the cutoff levels in the Swedish screening program for preterm infants. We chose to use a cutoff level of 400 nmol/L plasma in infants who were born before week 35 and 150 nmol/L for infants who were born in weeks 35 and 36. For detecting more patients, the cutoff level would have to be much lower, which would result in a number of false-positive tests that we consider to be unacceptably high. It is clear that neonatal screening cannot detect all infants with CAH. Some milder forms of the disease, just like in the past, will have to be diagnosed on the basis of clinical signs and symptoms.

Genotyping is a valuable diagnostic complement to neonatal screening for congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency

To evaluate genotyping as a diagnostic complement to neonatal screening for congenital adrenal hyperplasia, 91 children who had been diagnosed with this condition between 1986 and 1997 were analyzed for mutations in the steroid 21-hydroxylase gene. Screening levels of 17-hydroxyprogesterone were compared in patients representing different genotypes. Genotyping was performed using allele-specific PCR, the patients were divided into four groups according to the severity of their mutations, and screening results were compared between these groups as well as with 141 values representing false positive samples. The screening levels of 17-hydroxyprogesterone were significantly different in the five groups of samples. Values above 500 nmol/L were clearly associated with the most severe genotypes, whereas conclusions concerning disease severity could not be drawn from individual samples representing lower levels. For example, values around 150-200 nmol/L could be seen in children with all degrees of disease severity and could also constitute false positive samples. We conclude that genotyping is a valuable diagnostic tool and a good complement to neonatal screening, especially in confirming or discarding the diagnosis in cases with slightly elevated 17-hydroxyprogesterone levels. An additional benefit is that it provides information on disease severity, which reduces the risk of overtreatment of mildly affected children.

Failure of cortisone acetate treatment in congenital adrenal hyperplasia because of defective 11beta-hydroxysteroid dehydrogenase reductase activity

Congenital adrenal hyperplasia in children is often treated with cortisone acetate and fludrocortisone. It is known that certain patients with congenital adrenal hyperplasia require very high substitution doses of cortisone acetate, and a few patients do not respond to this treatment at all. A patient with 21-hydroxylase deficiency, for whom elevated pregnanetriol (P3) levels in urine were not suppressed during treatment with cortisone acetate (65 mg/m2 x day), was examined. The activation of cortisone to cortisol was assessed by measuring urinary metabolites of cortisone and cortisol. The patient's inability to respond to treatment with cortisone acetate was found to be caused by a low conversion of cortisone to cortisol, assumed to be secondary to low 11beta-hydroxysteroid dehydrogenase activity (11-oxoreductase deficiency). All exons and exon/intron junctions of the 11beta-hydroxysteroid dehydrogenase type1 gene (HSD11L) were sequenced without finding any mutations, but a genetic lesion in the promoter or other regulatory regions cannot be ruled out. The deficient 11-oxoreductase activity seems to have been congenital, in this case, but can possibly be attributable to a down-regulation of the enzyme activity. The results support the use of hydrocortisone, rather than cortisone acetate, for substitution therapy in adrenal insufficiency.

Benefits of neonatal screening for congenital adrenal hyperplasia (21-hydroxylase deficiency) in Sweden

OBJECTIVES

The aim of this study was to evaluate the benefits of neonatal screening for congenital adrenal hyperplasia (CAH).

METHODS

All children with CAH born in Sweden from January 1989 to December 1994 were subjected to a systematic follow-up. Clinical symptoms were recorded and laboratory data collected. The clinical diagnosis versus diagnosis by screening was investigated. The results were compared with those of a retrospective study of all patients diagnosed during 1969-1986 (before the introduction of neonatal screening).

RESULTS

The prevalence of CAH in Sweden was 1:9800 with screening. Patients with CAH were identified earlier by screening. Half of the infants (47%) were not diagnosed at the time of recall, which was 8 days (median). In the study population, 25% of the girls and 73% of the boys were diagnosed by screening alone. The median age at the time of the definite diagnosis in boys was 21 days before screening as compared with 9 days (median) during the last part of the screening period. During the screening period, only 1 boy had a severe salt loss crisis, which occurred at the age of 8 days. Before screening, (1969-1986) 2 boys had died in the neonatal period because of an adrenal crisis. The lowest serum sodium recorded at the time of diagnosis was 124 mmol/L (median; range, 93-148) before, as compared with 134 mmol/L (median; range, 115-148) after the introduction of screening. The number of girls who were initially considered to be boys was not reduced by screening (17% vs 18%). The period of uncertainty regarding gender attributable to virilization was shortened considerably, as well as the time it took to make a correct gender assignment: 23 days (median) before screening versus 3 days (median) with screening. The maximum time it took to make the correct gender assignment was 960 days before screening and 14 days with screening. The number of patients diagnosed late, ie, after the first year of life, decreased considerably after the introduction of screening. The false-positive rate (when a new filter paper blood sample was requested or when a child was referred to a pediatrician for follow-up) was <0.05% and in about 60% of the cases, it was attributable to preterm infants. The cost of screening was US dollar 2.70 per screened infant.

CONCLUSION

The main benefits of screening were avoidance of serious salt loss crises, earlier correct gender assignment in virilized girls, and detection of patients who would have otherwise been missed in the neonatal period. Deaths in the neonatal period were prevented by screening. The aim of the screening program was to identify patients with the severe forms of CAH. Nevertheless, it must be considered a distinct benefit that a number of patients with milder forms of CAH were detected earlier, because earlier therapy results in decreased virilization, normalized growth and puberty, and, in all probability, an improved psychosocial situation for these children. We conclude that, in the Swedish health care system, the benefits of screening for CAH outweigh the costs.

Identification of 11-dehydro-TXB2 as a suitable parameter for monitoring thromboxane production in the human

In order to identify suitable parameters for measurement of thromboxane production in vivo, the metabolism of TXB2 was studied in the human. [3H8]-TXB2 was given intravenously to a healthy human volunteer. Blood samples were collected for 50 min after the injection, and urine was collected for 24 hours. The urinary and blood metabolic profiles were visualized by the use of two-dimensional TLC and autoradiography. Identification of metabolites was achieved with GC/MS and in some cases by cochromatography with reference compounds in TLC and GC. In blood, unmetabolized TXB2 was the dominating compound during the first 30 min. Three less polar metabolites appeared, two of which were identified as 11-dehydro-TXB2 and 11,15-didehydro-13,14-dihydro-TXB2, respectively. The third compound was tentatively identified as 15-dehydro-13,14-dihydro-TXB2. Since 11-dehydro-TXB2 was one of the major metabolites in blood as well as urine, it was deemed suitable as target for measurement of thromboxane production in vivo. The advantages of 11-dehydro-TXB2 over its parent compound, TXB2, were demonstrated in experiments where unlabeled TXB2 was injected i.v. to a human volunteer, and the blood and urinary levels of both compounds were then followed by radioimmunoassay. Measured levels of 11-dehydro-TXB2 were found to give a more reliable picture of metabolic events than TXB2, the latter compound to a large extent reflecting technical difficulties during blood sample collection.

Circulating and urinary thromboxane B2 metabolites in the rabbit: 11-dehydro-thromboxane B2 as parameter of thromboxane production

The metabolism of thromboxane B2 was studied in the rabbit. The aim of the study was to identify metabolites in blood and urine that might serve as parameters for monitoring thromboxane production in vivo. [5,6,8,9,11,12,14,15-3H8]-Thromboxane B2 was administered by i.v. injection to rabbits, and blood samples and urine were collected with brief intervals. The metabolic profiles were visualized by two-dimensional thin layer chromatography and autoradiography, and the structures of five major metabolites were determined using chromatographic and mass spectrometric methods. In urine the major metabolites were identified as 11-dehydro-TXB2 and 2,3,4,5-tetranor-TXB1, and other prominent products were 11-dehydro-2,3,4,5-tetranor-TXB1, 2,3-dinor-TXB1 and 2,3-dinor-TXB2. In the circulation, TXB2 was found to disappear rapidly. The first major metabolite to appear was 11-dehydro-TXB2, which also remained a prominent product in blood for the remainder of the experiment (90 min). With time, the profile of circulating products became closely similar to that in urine. TXB2 was not converted into 11-dehydro-TXB2 by blood cells or plasma. The dehydrogenase catalyzing its formation was tissue bound and was found to have a widespread occurrence: the highest conversion was found in lung, kidney, stomach and liver. The results of the present study suggest that 11-dehydro-TXB2 may be a suitable parameter for monitoring thromboxane production in vivo in the rabbit in blood as well as urinary samples, and possibly also several tissues. This was also demonstrated in comparative studies using radioimmunoassays for TXB2 and 11-dehydro-TXB2.